Power source apparatus

ABSTRACT

This invention relates to a power source apparatus using piezoelectric elements.  
     A conventional power source apparatus using the piezoelectric element has an ability of generating less electricity, and therefore, has been applicable only to equipment which operates with low power consumption. To solve the problems of the conventional power source apparatus, the inventor has devised a “power source apparatus” and disclosed in Japanese Utility Model Registration No. 3074105. However, the devised power generating device has the Zener diode used as the trigger circuit determining the quantity of the charged electricity. Therefore, it is necessary to operate the trigger circuit all the time, consequently to use too much electricity to operate. The electrical power consumption therefor is unignorable compared with the electric energy generated by the piezoelectric element. The consumption of the unignorable quantity of electricity for monitoring the current with the Zener diode makes it impossible to charge a lot of electricity in the device. Thus, there has been room for further improvement in the devised power generating device used for electric power equipment having need of relatively high electricity.  
     In the light of the foregoing controversial points of the conventional power source apparatuses, the present invention has the aim of providing a power source apparatus using a piezoelectric element, which is capable of supplying sufficient electricity to an external device having need of relatively high electricity.  
     To attain the object described above according to the present invention, there is provided a power source apparatus comprising a power generating section for generating electricity by exerting a stress on piezoelectric elements, and a charging section for recharging therein with the electricity, which charging section includes a determination means for determining whether the quantity of charged electricity reaches a prescribed level according to the timing of generating electricity in the piezoelectric elements.  
     According to the apparatus, electricity is generated by exerting the stress on the piezoelectric elements and successively charged in the charging section, while increasing the quantity of charged electricity in the charging section. Only when the quantity of electricity charged in the charging section complies with the timing of power generation in the piezoelectric elements, i.e. the timing of increase of the quantity of charged electricity, a determination whether the quantity of charged electricity reaches the prescribed level is made. Thus, the desired determination of the charged electricity can be made intermittently with high efficiency according to the timing of increasing the charged electricity. As a result, more electricity can be charged without wasting of electricity for monitoring and determining the charged electricity.

TECHNICAL FIELD

[0001] This invention belongs to a technology relating to a power sourceapparatus using piezoelectric elements.

BACKGROUND ART

[0002] A technique for applying to a power source apparatus apiezoelectric element having a piezoelectric effect capable ofconverting mechanical energy into electric energy has been heretoforeproposed. There have been known various inorganic and organicpiezoelectric materials having the piezoelectric effect. Of thesepiezoelectric materials, a piezoelectric element formed of ceramic suchas PZT piezoelectric material has attracted attention in the field andput to practical use.

[0003] However, since the conventional piezoelectric element isdisadvantageously low in production of electricity, electrical energygenerated by the piezoelectric lacks in practicality for a powergenerating system. Thus, the conventional piezoelectric element could beused for low-power consumption equipment.

[0004] To resolve such a problem of the conventional piezoelectricelement, the inventor of the present invention has devised a “powergenerating device” as a power source apparatus using a piezoelectricelement, as described in Japanese Utility Model Registration No.3074105. The devised power generating device charges electric powergenerated by the piezoelectric element to a desired setting level anddischarge the charged electric power in an instant when it reaches thesetting level. The electric power energy discharged instantly can beapplied for a great range of applications having need of relatively highelectricity. In particular, the devised power generating devicecomprises a capacitor as a charging element, switching means forchanging over the operating state to discharge, and a Zener diodeserving as a trigger circuit connected to the switching means andcapacitor. When the electricity charged in the capacitor exceeds theprescribed constant voltage of the Zener diode, the switching means isoperated to discharge.

[0005] However, the devised power generating device has the Zener diodeused as the trigger circuit determining the quantity of the electricitycharged in the capacitor. Because the charged electricity in thecapacitor is determined according to the voltage of direct currentflowing into the capacitor, the direct current should be monitoredconstantly. Therefore, it is necessary to operate the trigger circuitall the time, consequently to use too much electricity to operate. Theelectrical power consumption therefor is unignorable compared with theelectric energy generated by the piezoelectric element. The consumptionof the unignorable quantity of electricity for monitoring the currentwith the Zener diode makes it impossible to charge a lot of electricityin the device. Thus, there has been room for further improvement in thedevised power generating device used for electric power equipment havingneed of relatively high electricity.

[0006] In the light of the foregoing controversial points of theconventional power source apparatuses, the present invention has thefollowing aims:

[0007] An object of the present invention is to provide a power sourceapparatus using a piezoelectric element, which is capable of supplyingsufficient electricity to an external device having need of relativelyhigh electricity.

[0008] Another object of the present invention is to provide a powersource apparatus capable of charging more electricity without wastingenergy for monitoring or determining charged electricity.

[0009] Still another object of the present invention is to provide apower source apparatus capable of generating a pseudo-alternatingcurrent for determining charged electricity.

DISCLOSURE OF THE INVENTION

[0010] To attain the objects described above according to the presentinvention, there is provided a power source apparatus comprising a powergenerating section for generating electricity by exerting a stress onpiezoelectric elements, and a charging section for recharging thereinwith the electricity, which charging section includes a determinationmeans for determining whether the quantity of charged electricityreaches a prescribed level according to the timing of generatingelectricity in the piezoelectric elements.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a block diagram showing a first embodiment of thepresent invention.

[0012]FIG. 2 is a block diagram showing in detail the first embodimentof the present invention.

[0013]FIG. 3 is a circuit diagram of the first embodiment of the presentinvention.

[0014]FIG. 4 is a sectional view showing a generating section in thefirst embodiment of the present invention.

[0015]FIG. 5 is a block diagram showing a second embodiment of thepresent invention.

[0016]FIG. 6 is a circuit diagram of the second embodiment of thepresent invention.

[0017]FIG. 7 is a sectional view showing a generating section in a thirdembodiment of the present invention.

BEST MODE FOR CARRYING OUT AN INVENTION

[0018] The power source apparatus according to the present inventioncomprises a power generating section for generating electricity byexerting a stress on piezoelectric elements, and a charging section forrecharging therein with the electricity, which charging section includesa determination means for determining whether the quantity of chargedelectricity reaches a prescribed level according to the timing ofgenerating electricity in the piezoelectric elements.

[0019] According to the apparatus, electricity is generated by exertingthe stress on the piezoelectric elements and successively charged in thecharging section, while increasing the quantity of charged electricityin the charging section. Only when the quantity of electricity chargedin the charging section complies with the timing of power generation inthe piezoelectric elements, i.e. the timing of increase of the quantityof charged electricity, a determination whether the quantity of chargedelectricity reaches the prescribed level is made.

[0020] The charging section also includes switching means for impedingdischarging from starting until a determination whether the quantity ofcharged electricity reaches the prescribed level is made.

[0021] According to the switching means, the quantity of chargedelectricity, which increases every time the electric power is generatedstepwise by the piezoelectric elements, is stored into the chargingsection without discharging until the quantity of charged electricity isdetermined to reach the prescribed level by the determination means.

[0022] The power generating section of the present invention is furtherprovided with a collision member, which comes into collision with thepiezoelectric elements. The determination means makes the determinationwhether the quantity of charged electricity reaches a prescribed levelaccording to the timing of generating electricity in the piezoelectricelements.

[0023] According to the structure with the collision member, thequantity of charged electricity generated due to the strain in thepiezoelectric element caused by bringing the collision member intocollision with the piezoelectric element increases substantiallystepwise. The, the determination whether the quantity of chargedelectricity reaches a prescribed level according to the timing ofcollision of the collision member with the piezoelectric element, i.e.the timing of increase of the quantity of charged electricity.

[0024] The determination means of the present invention performs theaforesaid determination by using alternating current output from thepiezoelectric element in generation of electricity.

[0025] The determination means makes it possible to observe the quantityof charge in the charging section by use of the alternating currentoutput from the piezoelectric element, which has a voltage proportionalto the quantity of charge, and make an intermittent determination by useof the alternating current generated only when causing strain in thepiezoelectric element (in the case of using the collision member, onlywhen bringing the collision member into collision with the piezoelectricelement).

[0026] Also, the determination means of the present invention makes theaforementioned determination by using alternating current generated in apseudo-manner and having the voltage proportional to the quantity ofcharge in the charging section.

[0027] According to the determination means, a pseudo-AC voltage havinga voltage proportional to the charged quantity is generated to fulfillthe observation and intermittent determination.

[0028] An embodiment of the power source apparatus according to thepresent invention will be described hereinafter with reference to theaccompanying drawings.

[0029]FIG. 1 is a block diagram showing the first embodiment of thepresent invention, FIG. 2 is a block diagram showing in detail the same,FIG. 3 is a circuit diagram of the same, and FIG. 4 is a sectional viewshowing a generating section in the same embodiment.

[0030] The power source apparatus 1 in the first embodiment of theinvention comprises the power generating section 2 for generatingelectricity by exerting a stress on the piezoelectric elements 21, andthe charging section 3 for recharging therein with the electricity. Thecharging section includes a determination means 33 for determiningwhether the quantity of charged electricity reaches a prescribed levelaccording to the timing of generating electricity in the piezoelectricelements 21.

[0031] That is, the power source apparatus 1 comprises the powergenerating section 2, the charging section 3, and an output section 4.The power generating section 2 is provided with the piezoelectricelements 21 and the collision member 22, which comes into collision withthe piezoelectric elements 2 to cause strain in the piezoelectricelements 21, consequently to generate electricity in the piezoelectricelements 21.

[0032] The charging section 3 has a rectification means 31, chargingmeans 32, and switching means 34 in addition to the determination means33. The rectification means 31 serves to rectify electricity having theAC voltage output from the power generating section 2 into a pulsatingcurrent. The charging means 32 is charged with the pulsating currentoutput as a direct current from the rectification means 31. Thedetermination means 33 has functions of intermittently monitoring anddetermining the quantity of the charged electricity in the chargingmeans 32 according to the timing of generating electricity in thepiezoelectric elements. This determination means consumes a little bitof electricity to monitor the charged electricity, but can furtherreduce consumption of electricity due to the intermittent determination.When confirming that the quantity of charged electricity reaches aprescribed level the switching means 34 brings the charging means 32into discharge. The electricity discharged from the charging means issupplied to an external device connected through the output section 4.

[0033] The sections constituting the power source apparatus of theinvention will be described hereinafter in detail with reference to FIG.3 and FIG. 4.

[0034] The power generating section 2 has the piezoelectric elementsattached to the opposite sides in a box-shaped housing 23, so as topermit the collision member 22 to roll between the piezoelectricelements and come into collision with the piezoelectric elements, asshown in FIG. 4. The collision member 22 is formed of a ball. As thepiezoelectric elements 21, there have been used two plates 211 and 212of PZT-piezoelectric ceramic, which are joined in reverse polarity, sothat a serial power generating mechanism can be formed so as to preventcounteraction due to the piezoelectric polarization thereof consequentlyto increase a power generation capacity thereof Each piezoelectricelement 21 is secured in part at its central part or both sides to aplate-like cushion member 25 with an adhesive 24 (or other fixing means)(the piezoelectric element is secured with the adhesive placed at thecentral part of the element in the case of FIG. 4). The cushion member25 is fixed on a housing with an adhesive 24. Therefore, thepiezoelectric ceramic plates 211 and 212 can sustain vibrational motionto increase the power generation efficiency and be protected from theimpact of the collision of the collision member 22 with thepiezoelectric element. On the both sides of the piezoelectric element21, there are formed membranous electrodes 29 having lead wires 261-264connected to the rectification means 31 disposed on the subsequentstage. The piezoelectric element 21 is provided on its front surface(with which the collision member 22 comes into collision) with alamelliform protector 27 for protecting the piezoelectric element fromthe impact of the collision member 22. Between the opposed piezoelectricelements 21, there is disposed a guide 28 for controlling the directionof the rotating motion of the collision member 22 so as to bring thecollision member 22 into accurate collision with the lamelliformprotectors 27 attached to the piezoelectric elements. In thisembodiment, the guide 28 is formed in a cylindrical shape, but may be ofa parting plate member.

[0035] The piezoelectric ceramic plates 211 and 212 are preferably madeof lead zirconate titanate, but the material of the piezoelectricelement is not specifically limited thereto. Besides, it is desirable tomake the piezoelectric ceramic plates 211 and 212 of as rigid materialas possible having high Q-value to fulfill higher generation ofelectricity. To be more specific, the material having a Q-value of over1000, preferably, over 2000, can be used suitably for the piezoelectricelement. The cushion member 25 may be suitably made of soft materialssuch as synthetic resin and rubber or composite material formed likesponge of these soft materials. To be more specific, polyethylene foamcan be suitably used for the cushion member. It is desirable to make thecollision member 22 of material of heavy enough not to break thepiezoelectric element 21 in order to increase the generating efficiency.To be more specific, there may be suitably used tungsten, steel or thelike. The protector 27 may be suitably made of phosphor bronze,stainless steel or the like. Since the phosphor bronze shows a goodprocessability, it is convenient for forming the protector.

[0036] The method for generating electricity by the power generatingsection 2 incorporating the piezoelectric elements 21 is by no meanslimited to that as described above. In the first embodiment, there aredisposed the two piezoelectric elements 21 on the opposite surfaces inthe power generating section 2 so as to allow the collision member 22 toroll therebetween and come into collision with the oppositepiezoelectric elements. However, one or three or more piezoelectricelements may be used in place of the two piezoelectric elements 21.Alternatively, there may be used two collision members as described inJapanese Patent Application Public Disclosure No. 2001-145375 in placeof the single collision member as above, or a collision member suspendedby spring means. The piezoelectric element may be formed by bonding asingle-layer piezoelectric ceramic plate 211 to a metal plate having athickness adjusted for balance in strain deformation, so as to generateelectricity by having the collision member collide with thepiezoelectric element from the side of the metal plate. Alternatively,the power generating section may be modified such that the collisionmember 22 is omitted, and instead, the piezoelectric element issupported at both sides so as to generate electricity by being pressed.The piezoelectric element 21 may be fixed at one end so as to generateelectricity by its free vibrations or vibrations in the form of othertype of strain (e.g. wave-formed vibrations).

[0037] The rectification means 31 has a full-wave rectifying circuitcomposed of diodes D1-D6 as shown in FIG. 3, to rectify the alternatingcurrent from the power generating section and output the rectifiedcurrent as a pulsating current to the subsequent stage. Of the leadwires 261-264 from the power generating section 2, the lead wires 262and 263 are connected to each other. The connected lead wires and otherlead wires are connected to the diodes D1-D6. Although the number oflead wires from the power generating section is reduced by connectingthe lead wires 262 and 263 to each other in this embodiment, thefull-wave rectify circuit may be constructed by separately connectingthe lead wires to eight diodes without connecting the lead wires 262 and263.

[0038] The charging means 32 is provided with a capacitor C1, which maybe replaced with a charging battery. While the pulsating current fromthe rectification means 31 is successively stored in the capacitor C1,the terminal voltage of the capacitor C1 is increased every time thecollision member 22 comes in collision with the piezoelectric element togenerate electricity

[0039] The switching means 34 is a self-holding type current switch. Theswitching means in the first embodiment employs complementarytransistors formed of a PNP transistor Tr1 and a NPN transistor Tr2. Theswitching means 34 is operated in such a manner that Tr1 is turned ON byapplying a voltage lower than that at a point “c” by about 0.6V (whichis determined by Tr1) to a point “b” in FIG. 3, and at about the sametime, Tr2 is also turned ON. When the switching means 34 turns ON,impedance between the points “c” and “d” shown in FIG. 3 turns out to bevery small. Then, the electricity charged in the capacitor C1 of thecharging means 32 is discharged to be output to an external devicethrough the output section 4 with an extremely small loss. The ON stateis self-held until ceasing discharging.

[0040] The determination means 33 includes capacitors C2 and C3 andresistances R1 and R2. The capacitor C3 is provided for prevention ofmalfunction. The capacitor C2 and the resistance R1 are disposed betweenthe point “a” through which the output from the piezoelectric element 21flows and the point “b” of the switching means 34. Time for applying thevoltage to the point “b” in determining the quantity of the electricitycharged in the capacitor is determined with a time constant obtainedherein. The alternating voltage occurs at the point “a” whenever thecollision member 22 comes into collision with the piezoelectric element21. This voltage corresponds to the sum of the interelectrode voltage ofthe capacitor C1 and the forward voltage of the diode D5. As the voltageincreases due to charging into the capacitor C1, the alternating voltageat the point “a” increases. That is, the alternating voltage at thepoint “a”, which is substantially proportional to the voltage of thedirect current at the both electrodes of the capacitor C1, occursintermittently whenever the collision member 22 comes into collisionwith the piezoelectric element. The alternating voltage at the point “a”is imposed on the point “b” for a very short time based on the timeconstant determined by the resistance R1 and capacitor C2. The voltageat the point “b” is determined according to the distribution ratio ofthe resistances R1 and R2, so that the switching means 34 turns ON whenthe voltage at the point “b” exceeds the voltage smaller than that atthe point “c” by about 0.6V (which is determined by Tr1). The voltage atthe point “b” is expressed by the equation [(Voltage at the point“c”)×(1−R2/(R1+R2))]. Consequently, the voltage lower than the voltageat the point “b” by about 0.6V (Voltage at the point “b”-about 0.6V) isdetermined as a threshold value of the switching means, with which thelevel of the charged quantity is measured Thus, the charged level forinitiating discharging can be arbitrarily set by adjusting R1 and R2. Inthis embodiment, the point “a” is placed on the side of the lead wire264, but may be placed on the side of the lead wire 261 or lead wires262 and 263 connected thereto. Of the two piezoelectric elements, thepiezoelectric element 21 serves to make the determination with thegeneration of electricity in the illustrated embodiment, but both thepiezoelectric elements 21 may have a function of making thedetermination. The determination may be made once every N-times thepiezoelectric element 21 generates electricity (where N is an arbitrarynumber).

[0041] The output section 4 is provided with a connector and the likefor connecting the apparatus to an external device. Namely, theelectricity charged in the apparatus is output to the external devicethrough the output section 4 at a burst.

[0042] The operation of the first embodiment described above will bedescribed. First, when the power generating section 2 receivesoscillating movement or other movement, the collision member 22 comesinto collision with the piezoelectric element 21 to cause strain on thepiezoelectric element 21, consequently generating alternating voltage.Since the power generating section 2 has the opposed piezoelectricelements 21, the generation of electricity can be efficiently carriedout. The alternating power thus generated is rectified into a pulsatingcurrent by the rectification means 31 in the charging section 3 andcharged in the form of a direct current into the charging means 32. Thequantity of charged electricity in the charging means 32 graduallyincreases as the collision of the collision member 22 with thepiezoelectric elements 21 are repeated.

[0043] The alternating voltage intermittently occurs at the point “a”every time the collision member 22 comes into collision with one of thepiezoelectric elements 21. The alternating voltage at the point “a”increases with the increase of the quantity of electricity charged inthe charging means 32. When the alternating voltage occurs at the point“a”, voltage is imparted to the point “b” for a very short time based onthe time constant determined by the resistance R1 and capacitor C2. Whenthe voltage imparted to the point “b” becomes above the prescribedvalue, the switch means 34 turns ON and is kept in the self-holdingstate. Consequently, the electricity charged in the charging means 32can be discharged to the external device at a burst.

[0044] When the electricity charged in the charging means 32 is consumedin the external device to reduced close to zero, the self-holding stateof the switching means is automatically released, consequently to startcharging in the charging means 32.

[0045] The determination means 33 in this embodiment makes intermittentdetermination of the quantity of charge at the timing of the collisionof the collision member 22 with the piezoelectric element 21. When thequantity of charge exceeds the prescribed level, the switching means 34turns ON to discharge the electricity charged in the charging means.That is, unless the collision member 22 comes into collision with thepiezoelectric element 21, the determination of the quantity of charge isnot made, thus to need little electricity to monitor the quantity ofcharge. The electricity charged in the charging means is discharged at aburst at the moment the electricity charged reaches the prescribedlevel, so that large electric power can be supplied to the externaldevice.

[0046] As the external device to which the power source apparatus 1according to the present invention is connected, there may be suitablyapplied electronic devices operating for a fixed period of time, such ashigh-intensity lights and LEDs.

[0047] Thus, the alternating voltage is produced from the electricity,which is obtained from the piezoelectric element 21 every time thecollision member 22 comes into collision with the piezoelectric element21, and utilized for determining whether or not the quantity of chargedelectricity in the charging means 32 reaches the prescribed level. Theintermittent determination of the quantity of charge prevents wasting ofelectricity for monitoring the charged electricity, consequently toincrease the charging efficiency of the charging means 32. Therefore,the power source apparatus of the invention can be used as ahigh-performance power source for an external device having need ofrelatively high electricity, even in case of employing inefficientpiezoelectric elements 21.

[0048] Next, the second embodiment of the power source apparatusaccording to the present invention will be described with reference tothe accompanying drawings. FIG. 5 is a block diagram showing in detailthe second embodiment of the invention, and FIG. 6 is a circuit diagramof the second embodiment of the invention. Since the second embodimentof the invention is a modification of the first embodiment as describedabove, the component elements assigned by the same reference numerals asthose in the first embodiment will not be described further here.

[0049] The alternating voltage, which is used at the point “a” for thedetermination means 33 of the power source apparatus in the firstembodiment, is generated in the form of quasi-voltage in accordance withthe quantity of charge to make the intended determination in the secondembodiment.

[0050] The charging section 3 in the second embodiment includes amechanical switch Sw1 as alternating-current generating means 35, whichoperates in cooperation with the power generating section 2. Themechanical switch Sw1 has two terminals, one connected to the capacitorC1 in the charging means 32 and the other connected to the capacitor C2in the determination means 33. The mechanical switch Sw1 is turned onand off with the oscillating movement of the power generating section 2,consequently to intermittently send the interelectrode voltage of thecapacitor C1 in the charging means 32 as a pseudo-AC voltage to thecapacitor C2. In the meantime, the voltage is imposed to the point “b”for a very short time based on the time constant determined by thecapacitor C2 and resistance R1. Then, when the voltage imposed to thepoint “b” exceeds the prescribed level, the switching means 34 isoperated in the same manner as the first embodiment described above,thereby to discharge the discharging means 32.

[0051] Thus, the second embodiment can as well fulfill the operation andeffect of the first embodiment by generating the pseudo-AC voltage.

[0052] Next, the power source apparatus in the third embodiment of thepresent invention will be described with reference to FIG. 7 showing, insection, the power generating section. Since the third embodiment of theinvention is a modification of the first embodiment as described above,the component elements assigned by the same reference numerals as thosein the first embodiment will not be described further here.

[0053] The third embodiment is featured by the power generating section20 having the piezoelectric elements 21 connected in parallel,differently from the first embodiment in which the piezoelectricelements 2 are connected in series. Each piezoelectric element 21 hastwo piezoelectric ceramic plates 211 and 212 joined to each other in thesame direction in polarization. An electrode 292 is united to betweenthe piezoelectric ceramic plates 211 and 212. The electrode 292 lookslarger than the actual thickness in the illustration of FIG. 7 foreasier comprehension, but it is made of metal plate of very thin (about10 to 50 μm) in fact and, preferably, material encountering littlemechanical resistance in causing strain on the piezoelectric element 21.To be more specific, the electrode may preferably be made of phosphorbronze, brass or the like. Onto the outside surfaces of thepiezoelectric ceramic plates 211 and 212, which are opposite to thesurfaces joined to the electrode 292, there are attached electrodes 291.To each electrode 292, a lead wire 262 (264) is connected, and to eachelectrode 291, a lead wire 261 (263) is connected. These lead wires areconnected to the subsequent stage in the same manner as shown in FIG. 3.Other components are identical with those in the first embodimentdescribed above.

[0054] The parallel-type power generating system having thepiezoelectric elements connected in parallel as noted above has thepower generation efficiency about twice as high as that of theserial-type system having the piezoelectric elements connected inseries. That is, this parallel-type power generating system applied forcharging a capacitor has an efficient capacitance capable of dischargingelectricity as much as the serial-type power generating system with halfthe driving energy required for operating the serial-type powergenerating system.

[0055] Although the power source apparatus 1 in each of the first tothird embodiments is configurated so as to be connected to the externaldevice by way of example, it may of course be incorporated as a powersource means in any electronic devices.

[0056] <Industrial Applicability>

[0057] The power source apparatus according to the present invention hasan advantageous feature capable of determining electricity generated bythe piezoelectric elements and charged in the charging means accordingto the timing of generating electricity in the piezoelectric elements.Therefore, determination whether the quantity of electricity charged inthe charging means reaches the prescribed level can be madeintermittently with high efficiency according to the timing ofincreasing the charged electricity, but not carried out consecutively.As a result, more electricity can be charged without wasting ofelectricity for monitoring and determining the charged electricity.

[0058] Since the power source apparatus of the invention has theswitching means for impeding discharging from starting until adetermination whether the quantity of charged electricity reaches theprescribed level is made, the electricity charged to the requiredquantity in the charging means can be discharged at a burst. Thus, eventhe power source apparatus using the piezoelectric elements can be usedas a power source for an external device having need of high power andapplied to a broad range of equipment or devices.

1. A power source apparatus comprising a power generating section forgenerating electricity by exerting a stress on piezoelectric elements,and a charging section for recharging therein with the electricity,which charging section includes a determination means for determiningwhether the quantity of charged electricity reaches a prescribed levelaccording to the timing of generating electricity in said piezoelectricelements.
 2. The power source apparatus according to claim 1, whereinsaid charging section includes switching means for impeding dischargingfrom starting until a determination whether the quantity of chargedelectricity reaches the prescribed level is made.
 3. The power sourceapparatus according to claim 1, wherein said power generating sectionincludes a collision member coming into collision with the piezoelectricelements, and said determination means makes the determination whetherthe quantity of charged electricity reaches a prescribed level accordingto the timing of generating electricity in said piezoelectric elements.4. The power source apparatus according to claim 1, wherein saiddetermination means makes the determination by using alternating currentoutput from said piezoelectric element in generation of electricity. 5.The power source apparatus according to claim 2, wherein saiddetermination means makes the determination by using alternating currentoutput from said piezoelectric element in generation of electricity. 6.The power source apparatus according to claim 3, wherein saiddetermination means makes the determination by using alternating currentoutput from said piezoelectric element in generation of electricity. 7.The power source apparatus according to claim 1, wherein saiddetermination means makes the determination by using alternating currentgenerated in a pseudo-manner and having the voltage proportional to thequantity of charge in said charging section.
 8. The power sourceapparatus according to claim 2, wherein said determination means makesthe determination by using alternating current generated in apseudo-manner and having the voltage proportional to the quantity ofcharge in said charging section.
 9. The power source apparatus accordingto claim 3, wherein said determination 5 means makes the determinationby using alternating current generated in a pseudo-manner and having thevoltage proportional to the quantity of charge in said charging section.10. The power source apparatus according to claim 2, wherein said powergenerating section includes a collision member coming into collisionwith the piezoelectric elements, and said determination means makes thedetermination whether the quantity of charged electricity reaches aprescribed level according to the timing of generating electricity insaid piezoelectric elements.